In applied electro-chemistry electrolytic cells of different designs are widely used for preparing products of anode oxidation of chloride solutions, in particular electrolytic cells with coaxial cylindrical electrodes and a diaphragm between them (see, for example Japanese patent JP 02274889 A, C25B 9/00, 1989).
Module electrolytic are more perspective as they provide for required productivity by connecting required number of electrolytic cells, decreased cost of designing and production of electrolytic sections of selected productivity, unification of assemblies and parts, decreased time for mounting and repairing such electrolytic sections (see, for example patent U.S. Pat. No. 5,635,040 C02F 1/461, Mar. 6, 1997).
A device for producing anodic oxidation products of an alkali metal chloride solutions is known in the prior art. The device comprises at least one electrolytic cell with coaxial cylindrical electrodes divided with a diaphragm into an anode and cathode chambers, an anode and cathode circulation circuits each provided with a gas separation volume, a pipeline for supplying alkali metal chloride solution connected to the anode circulation circuit and the system for maintaining increased pressure in the anode circuit. A gas separation volume outlet of the anode circuit can be connected to a mixer for producing oxidation products not only in gas state but also as an aqueous solution (see patent RU 2088693, C25B 9/00, 1997).
The known device is configured according to module concept. It is easy to be mounted for different production level depending on required products to be obtained in gas or solution state. However this device is relatively bulky, has two circulation circuits. Moreover, the size and height of the gas separation volumes should follow additional requirements in relation to the cells resulting in increase of device size. Materials for pipes and assemblies forming the anode circulation circuit must also follow special requirements since during operation they are subjected to continuous action of extremely chemically hostile gas-liquid medium flowing at a high speed. Presence of two circulation circuits with many hydraulic joints also increases the risk of depressurization.
The closest device in technology and technical result is a device for obtaining products of alkali or alkaline-earth chloride solution anode oxidation. The device comprises at least one electrochemical reactor composed of a few modular electrochemical cells each including coaxial cylindrical electrodes, an inner hollow anode and an outer cathode, and a diaphragm between them. The diaphragm is made of a ceramic based on zirconium, aluminum and yttrium oxides. The electrodes are arranged in lower and upper mounting units so that a hydraulically isolated anode chamber and a cathode chamber are formed; the chambers having an inlet in the lower mounting unit and an outlet in the upper mounting unit, wherein the inlet and outlet of the anode chamber are in communication with the anode hollow and the anode has perforations arranged in the upper and lower parts as well as evenly along the length of the anode. The cells of the reactor or reactors are of one type, the anode and cathode are at an interelectrode distance of 8-10 mm, wherein:
d=1.5-2.3 interelectrode distance
D=3.0-4.3 interelectrode distance
Ld=25-40 interelectrode distance
δ=0.15-0.35 interelectrode distance and Sk≧Sa, wherein
d is the outer diameter of the anode;
D is the inner diameter of the cathode;
Ld is the length of the cathode;
δ is the thickness of diaphragm side walls;
Sk is the cross section area of the cathode chamber; and
Sa is the cross section area of the anode chamber.
The cells are provided with input lines to cathode and anode chambers and output lines from cathode and anode chambers; the lines are connected to the lower and upper mounting units correspondingly. The cells of the reactor are arranged at one level and hydraulically connected in parallel. The device further comprises a supply line with a pump for supplying initial solution under pressure, a manifold of initial solution connected to the initial solution supply line and the input lines to the anode chambers of the cells, a manifold for gaseous products of anode oxidation connected to output lines from the anode chambers of the cells, a cathode circulation circuit connected to the input and output lines of the cell cathode chambers, and a separation tank for separating gas escaping during electrolysis, an upstream pressure controller connected to the manifold of anode oxidation gaseous products and an output line for gaseous products from the anode chamber connected to the upstream pressure controller, a controller of chloride solution level in the anode chambers (see RU 2176989). This technical solution has been chosen by the inventors as a prototype.
Use of the solution according to the prototype allows deleting the anode circulation circuit thereby making the device simpler and cheaper.
However the known solution has some disadvantages. The cells of a reactor or reactors work in different hydraulic conditions though arranged at one level due to different length of the hydraulic line for each cell of the reactor relative to common places of connections to the device hydraulic system. It results in irregular thermal conditions of cells, different chemical compositions of anode oxidation products obtained in cells of the same reactor and irregular wear of the electrocatalytic coating of anodes in cells. What is more, the device has relatively low productivity of cells in the amount of anode oxidation products compared to calculated value due to high heating. In the known device there is high risk of premature wear of cell electrodes due to leakage current through electrolyte solutions filling the hydraulic lines combining cells into a reactor.